Method test_product

Lib/test/test_itertools.py:1042–1102

(self)

        check(4, [(([2], [3]), [4])])

    def test_product(self):
        for args, result in [
            ([], [()]),                     # zero iterables
            (['ab'], [('a',), ('b',)]),     # one iterable
            ([range(2), range(3)], [(0,0), (0,1), (0,2), (1,0), (1,1), (1,2)]),     # two iterables
            ([range(0), range(2), range(3)], []),           # first iterable with zero length
            ([range(2), range(0), range(3)], []),           # middle iterable with zero length
            ([range(2), range(3), range(0)], []),           # last iterable with zero length
            ]:
            self.assertEqual(list(product(*args)), result)
            for r in range(4):
                self.assertEqual(list(product(*(args*r))),
                                 list(product(*args, **dict(repeat=r))))
        self.assertEqual(len(list(product(*[range(7)]*6))), 7**6)
        self.assertRaises(TypeError, product, range(6), None)

        def product1(*args, **kwds):
            pools = list(map(tuple, args)) * kwds.get('repeat', 1)
            n = len(pools)
            if n == 0:
                yield ()
                return
            if any(len(pool) == 0 for pool in pools):
                return
            indices = [0] * n
            yield tuple(pool[i] for pool, i in zip(pools, indices))
            while 1:
                for i in reversed(range(n)):  # right to left
                    if indices[i] == len(pools[i]) - 1:
                        continue
                    indices[i] += 1
                    for j in range(i+1, n):
                        indices[j] = 0
                    yield tuple(pool[i] for pool, i in zip(pools, indices))
                    break
                else:
                    return

        def product2(*iterables, repeat=1):
            'Pure python version used in docs'
            if repeat < 0:
                raise ValueError('repeat argument cannot be negative')
            pools = [tuple(pool) for pool in iterables] * repeat

            result = [[]]
            for pool in pools:
                result = [x+[y] for x in result for y in pool]

            for prod in result:
                yield tuple(prod)

        argtypes = ['', 'abc', '', range(0), range(4), dict(a=1, b=2, c=3),
                    set('abcdefg'), range(11), tuple(range(13))]
        for i in range(100):
            args = [random.choice(argtypes) for j in range(random.randrange(5))]
            expected_len = prod(map(len, args))
            self.assertEqual(len(list(product(*args))), expected_len)
            self.assertEqual(list(product(*args)), list(product1(*args)))